Associations of age with serum insulin, proinsulin and the proinsulin-to-insulin ratio: a cross-sectional study

Prospective risk of Type 2 diabetes in 99 892 Nordic women with polycystic ovary syndrome and 446 055 controls: national cohort study from Denmark, Finland, and Sweden

STUDY QUESTION

What is the prospective risk of Type 2 diabetes (T2D) in Nordic women with polycystic ovary syndrome (PCOS) compared to controls?

SUMMARY ANSWER

A diagnosis of PCOS and BMI ≥30 kg/m2 is a high-risk phenotype for a prospective risk of T2D diagnosis across Nordic countries.

WHAT IS KNOWN ALREADY

The risk of T2D in women with PCOS is increased. The risk of T2D is related to BMI and the magnitude of risk in normal weight women with PCOS has been discussed. However, prospective data regarding risk of T2D in population-based cohorts of women with PCOS are limited.

STUDY DESIGN, SIZE, DURATION

This national register-based study included women with PCOS and age-matched controls. The main study outcome was T2D diagnosis occurring after PCOS diagnosis. T2D was defined according to ICD-10 diagnosis codes and/or filled medicine prescriptions of anti-diabetic medication excluding metformin.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study cohort included women originating from Denmark (PCOS Denmark, N = 27 016; controls, N = 133 994), Finland (PCOS Finland, N = 20 467; controls, N = 58 051), and Sweden (PCOS Sweden, N = 52 409; controls, N = 254 010). The median age at cohort entry was 28 years in PCOS Denmark, Finland, and Sweden with a median follow-up time (interquartile range) in women with PCOS of 8.5 (4.0-14.8), 9.8 (5.1-15.1), and 6.0 (2.0-10.0) years, respectively. Cox regression analyses were adjusted for BMI and length of education.

MAIN RESULTS AND THE ROLE OF CHANCE

The crude hazard ratio (HR, 95% CI) for T2D diagnosis in women with PCOS was 4.28 (3.98-4.60) in Denmark, 3.40 (3.11-3.74) in Finland, and 5.68 (5.20-6.21) in Sweden. In adjusted regression analyses, BMI ≥30 vs <25 kg/m2 was associated with a 7.6- to 11.3-fold risk of T2D. In a combined meta-analysis (PCOS, N = 99 892; controls, N = 446 055), the crude HR for T2D in PCOS was 4.64 (3.40-5.87) and, after adjustment for BMI and education level, the HR was 2.92 (2.32-3.51).

LIMITATIONS, REASONS FOR CAUTION

Inclusion of more severe cases of PCOS in the present study design could have lead to an overestimation of risk estimates in our exposed population. However, some women in the control group would have undiagnosed PCOS, which would lead to an underestimation of T2D risk in women with PCOS. BMI data were not available for all participants. The present study should be repeated in study cohorts with higher background risks of T2D, particularly in populations of other ethnicities.

WIDER IMPLICATIONS OF THE FINDINGS

The prospective risk for diagnosis of T2D is increased in women with PCOS, and the risk is aggravated in women with BMI ≥30 kg/m2.

STUDY FUNDING/COMPETING INTEREST(S)

Funding in Denmark was from the Region of Southern Denmark, Overlægerådet, Odense University Hospital. Funding in Finland was from Novo Nordisk Foundation, Finnish Research Council and Sigrid Juselius Foundation, the National Regional Fund, Sakari Alhopuro Foundation and Finnish Diabetes Research Foundation. E.E. has received a research grant from Ferring Pharmaceuticals (payment to institution) and serves as medical advisor for Tilly AB, not related to this manuscript. The remaining authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

A computational model of Alzheimer's disease at the nano, micro, and macroscales

Introduction

Mathematical models play a crucial role in investigating complex biological systems, enabling a comprehensive understanding of interactions among various components and facilitating in silico testing of intervention strategies. Alzheimer's disease (AD) is characterized by multifactorial causes and intricate interactions among biological entities, necessitating a personalized approach due to the lack of effective treatments. Therefore, mathematical models offer promise as indispensable tools in combating AD. However, existing models in this emerging field often suffer from limitations such as inadequate validation or a narrow focus on single proteins or pathways.

Methods

In this paper, we present a multiscale mathematical model that describes the progression of AD through a system of 19 ordinary differential equations. The equations describe the evolution of proteins (nanoscale), cell populations (microscale), and organ-level structures (macroscale) over a 50-year lifespan, as they relate to amyloid and tau accumulation, inflammation, and neuronal death.

Results

Distinguishing our model is a robust foundation in biological principles, ensuring improved justification for the included equations, and rigorous parameter justification derived from published experimental literature.

Conclusion

This model represents an essential initial step toward constructing a predictive framework, which holds significant potential for identifying effective therapeutic targets in the fight against AD.

Serum proinsulin levels as peripheral blood biomarkers in patients with cognitive impairment

Insulin has long been associated with dementia. Insulin affecting the clearance of amyloid-β peptide and phosphorylation of tau in the CNS. Proinsulin is a precursor of insulin and its elevated serum levels are associated with peripheral insulin resistance that may reduce brain insulin levels. Our study aimed to assess differences in serum proinsulin levels between normal and cognitive impairment groups. Prospective recruitment of elderly participants was initiated from October 2019 to September 2023. Patients were divided into "cognitive impairment" and "normal cognition" group. All participants had blood drawn and serum proinsulin was measured at baseline and 12 months. Neurocognitive testing was performed every 6 months. A total of 121 participants were recruited. Seventy-seven were in the normal cognition group and 44 in the cognitive impairment group. The glycemic control and prevalence of diabetes type 2 was similar between groups. Baseline serum proinsulin levels were higher in the cognitively impaired group compared to the normal group at baseline (p = 0.019) and correlated with worse cognitive scores. We identified cognitive status, age, and BMI as potential factors associated with variations in baseline proinsulin levels. Given the complex interplay between insulin and dementia pathogenesis, serum biomarkers related to insulin metabolism may exhibit abnormalities in cognitive impaired patients. Here we present the proinsulin levels in individuals with normal cognitive function versus those with cognitive impairment and found a significant difference. This observation may help identifying non-diabetic patients suitable for treatment with novel AD drugs that related to insulin pathway.

Prospective Risk of Type 2 Diabetes in Normal Weight Women with Polycystic Ovary Syndrome

Background: Polycystic ovary syndrome (PCOS) is associated with obesity and increased risk for type 2 diabetes (T2D). However, the prospective risk of T2D in normal weight women with PCOS is debated, together with the relevant prospective screening programs for T2D in normal weight women with PCOS. Aim: To review and discuss prospective risk of T2D in normal weight women with PCOS, and to give recommendations regarding prospective screening for T2D in normal weight women with PCOS. Methods: Systematic review. Results: A systematic literature search resulted in 15 published prospective studies (10 controlled studies and 5 uncontrolled studies) regarding risk of T2D in study cohorts of PCOS, where data from normal weight women with PCOS were presented separately. In controlled studies, higher risk of T2D in normal weight women with PCOS compared to controls was reported in 4/10 studies, which included one study where T2D diagnosis was based on glucose measurement, two register-based studies, and one study where diagnosis of T2D was self-reported. Six of the 10 controlled studies reported no increased risk of T2D in normal weight women with PCOS. Four of these studies based the diagnosis of T2D on biochemical measurements, which supported the risk of surveillance bias in PCOS. In uncontrolled studies, 2/5 reported a higher risk of T2D in lean women with PCOS compared to the general population. We discuss the evidence for insulin resistance and β-cell dysfunction in normal weight women with PCOS, and aggravation in the hyperandrogenic phenotype, ageing women, and women with Asian ethnicity. Impaired glucose tolerance could be an important metabolic and vascular risk marker in PCOS. Conclusions: The risk of T2D may be increased in some normal weight women with PCOS. Individual risk markers such as hyperandrogenism, age >40 years, Asian ethnicity, and weight gain should determine prospective screening programs in normal weight women with PCOS.

Endoplasmic Reticulum (ER) Stress and Its Role in Pancreatic β-Cell Dysfunction and Senescence in Type 2 Diabetes

An increased life span and accompanying nutritional affluency have led to a rapid increase in diseases associated with aging, such as obesity and type 2 diabetes, imposing a tremendous economic and health burden on society. Pancreatic β-cells are crucial for controlling glucose homeostasis by properly producing and secreting the glucose-lowering hormone insulin, and the dysfunction of β-cells determines the outcomes for both type 1 and type 2 diabetes. As the native structure of insulin is formed within the endoplasmic reticulum (ER), ER homeostasis should be appropriately maintained to allow for the proper metabolic homeostasis and functioning of β-cells. Recent studies have found that cellular senescence is critically linked with cellular stresses, including ER stress, oxidative stress, and mitochondrial stress. These studies implied that β-cell senescence is caused by ER stress and other cellular stresses and contributes to β-cells’ dysfunction and the impairment of glucose homeostasis. This review documents and discusses the current understanding of cellular senescence, β-cell function, ER stress, its associated signaling mechanism (unfolded protein response), and the effect of ER stress on β-cell senescence and dysfunction.

Value of simple clinical parameters to predict insulin resistance among newly diagnosed patients with type 2 diabetes in limited resource settings

Background

Insulin resistance (IR) has been considered as a therapeutic target in the management of type 2 diabetes mellitus (T2DM). Readily available, simple and low cost measures to identify individuals with IR is of utmost importance for clinicians to plan optimal management strategies. Research on the associations between surrogate markers of IR and routine clinical and lipid parameters have not been carried out in Sri Lanka, a developing country with rising burden of T2DM with inadequate resources. Therefore, we aimed to study the utility of readily available clinical parameters such as age, body mass index (BMI), waist circumference (WC) and triglyceride to high density lipoprotein cholesterol ratio (TG/HDL-C) in the fasting lipid profile in predicting IR in a cohort of patients with newly diagnosed T2DM in Sri Lanka.

Methods and findings

We conducted a community based cross sectional study involving of 147 patients (age 30–60 years) with newly diagnosed T2DM in a suburban locality in Galle district, Sri Lanka. Data on age, BMI, WC, fasting plasma glucose (FPG) concentration, fasting insulin concentration and serum lipid profile were collected from each subject. The indirect IR indices namely homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI) and McAuley index (MCA) were estimated. Both clinical and biochemical parameters across the lowest and the highest fasting insulin quartiles were compared using independent sample t-test. Linear correlation analysis was performed to assess the correlation between selected clinical parameters and indirect IR indices. The area under the receiver operating characteristic (ROC) curve was obtained to calculate optimal cut-off values for the clinical markers to differentiate IR. BMI (p<0.001) and WC (p = 0.01) were significantly increased whereas age (p = 0.06) was decreased and TG/HDL-C (p = 0.28) was increased across the insulin quartiles. BMI and WC were significantly correlated (p<0.05) with HOMA, QUICKI and MCA. Out of the clinical parameters, age showed a borderline significant correlation with QUICKI and TG/HDL-C showed a significant correlation only with MCA. The area under ROC of BMI was 0.728 (95% CI 0.648–0.809; p<0.001) and for WC, it was 0.646 (95% CI 0.559–0.734; p = 0.003). The optimized cut-off value for BMI and WC were 24.91 kg/m² and 81.5 cm respectively to differentiate the patients with IR or ID. Study limitations include small sample size due to recruitment of patients only from a limited geographical locality of the country and not totally excluding of the possibility of inclusion of some patients with slowly progressive type 1 DM or Latent onset diabetes of adulthood from the study population.

Conclusions

The results revealed that there was a significant positive correlation between BMI, WC and HOMA while a significant negative correlation with QUICKI and MCA among the cohort of patients with newly diagnosed T2DM. The cut-off values of BMI and WC as 24.91 kg/m² and 81.5 cm respectively could be used as simple clinical parameters to identify IR in newly diagnosed patients with T2DM. Our results could be beneficial in rational decision making in the management of newly diagnosed patients with T2DM in limited resource settings.

The Influence of Hypertensive Therapies on Circulating Factors: Clinical Implications for SCFAs, FGF21, TNFSF14 and TNF-α

Studying the role of circulatory factors in the pathogenesis of diseases has been key to the development of effective therapies. We sought to examine the effect of antihypertensive therapies on numerous circulatory factors including short chain fatty acids and growth factors in a human cohort. A subset of participants from an earlier study was characterized by their hypertensive and/or treatment status and separated into three groups: (i) normotensives; (ii) untreated hypertensive and (iii) treated hypertensive subjects. Circulating levels of short chain fatty acids, FGF21 and TNF superfamily members were measured as part of this study. Both F2-isoprostane and circulating lipid levels were reanalysed as part of this current study. We found that antihypertensive treatment increased butyrate levels and decreased acetate levels to levels similar to normotensives. We also found that antihypertensive treatments reduced levels of circulating FGF21, TNFSF14 and TNF-α. In conclusion, we identified several circulatory factors that are altered in hypertension.

Subgroup analysis of proinsulin and insulin levels reveals novel correlations to metabolic indicators of type 2 diabetes

Proinsulin, insulin and proinsulin/insulin (P/I) ratio have been reported to be correlated with fasting plasma glucose (FPG) and Hemoglobin A1c (HbA1c) in whole population study therefore sensitive predictors of T2D progression. However, by analyzing data collected from 2018-2019 from a cohort of 1579 East Asian individuals from Hainan Province of China, we find that the associations of proinsulin, insulin and P/I ratio with diabetic indicators have distinct, sometimes opposite regression patterns in normal, prediabetic and diabetic subgroups. The strength of the associations are generally weak in normal and prediabetic groups, and only moderate in diabetic group between postprandial proinsulin and HbA1c, between postprandial insulin and FPG or HbA1c, and between postprandial P/I ratio and FPG or HbA1c. Receiver operating characteristic (ROC) curve analysis shows these parameters are weaker than age in predicting diabetes development, with P/I ratio being the weakest. Proinsulin and insulin levels are tightly associated with insulin sensitivity across all subgroups, as measured by Matsuda index. Together, our results suggest that proinsulin, insulin or P/I ratio are weak predictors of diabetes development in the whole population, urging the need for stratifying strategies and novel perspectives in evaluating and predicting hyperglycemia progression.

Health risks and interventions in prediabetes: A review

Prediabetes is a condition which appears prior to the development of diabetes in which blood glucose is abnormally high but do not reach the diagnostic threshold of type 2 diabetes mellitus. It is characterized by a cluster of metabolic abnormalities viz. dysglycemia, dyslipidemia, hypertension, physical inactivity, obesity, insulin resistance, procoagulant state, endothelial dysfunction, oxidative stress and inflammation, placing prediabetic subjects to an increased risk for diabetes and its complications. Recent studies demonstrate that complications of diabetes i.e. microvascular and macrovascular complications may manifest in some prediabetic subjects. This article reviews prediabetes-related risk factors and health issues. In addition, this article also highlights the interventions to prevent the development of diabetes in prediabetic subjects.

Sex-Based Differences in Diabetes Prevalence and Risk Factors: A Population-Based Cross-Sectional Study Among Low-Income Adults in China

Aims: The prevalence of diabetes mellitus (DM) among adults has reached epidemic proportions worldwide, including China. In China, sex-based differences in the prevalence and risk factors of DM may exist, particularly among low-income individuals. Thus, we assessed these differences in the prevalence of DM and its risk factors in a low-income Chinese population. Materials and Methods: Residents aged ≥45 years without histories of strokes or cardiovascular disease were recruited for this study. Multivariate logistic regression analyses were performed to assess the association of risk factors with DM prevalence. Results: This study included 3,725 participants (41.2%, men; 58.8%, women). The mean age of the women (61.12 years) was higher than that of the men (59.14 years, P < 0.001). There was no significant sex-based difference in DM prevalence (men, 14.1%; women, 14.5%). Overweight, obesity, high triglyceride levels, and hypertension were independent risk factors for DM in both sexes. However, high-density lipoprotein-cholesterol levels were negatively associated with DM risk among men [odds ratio (OR), 0.544; 95% confidence interval (CI), 0.355-0.833; P = 0.005]. Among women, advanced age and high low-density lipoprotein-cholesterol levels were independent risk factors for DM; there was a higher DM risk for women aged 55-74 years than for those aged 45-54 years; however, physical activity was associated with an increased risk of DM (OR, 1.705; 95% CI, 1.195-2.432; P = 0.003). Conclusions: These findings suggest a crucial need to implement individualized blood pressure, weight, and lipid managements in low-income populations in China to reduce the burden of DM, especially among older women.

Beta cell stress in a 4-year follow-up of patients with type 2 diabetes: A longitudinal analysis of the BetaDecline Study

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with a progressive deterioration in beta cell function and loss of glycaemic control. Clinical predictors of beta cell failure are needed to guide appropriate therapy.

METHODS

A prospective evaluation of a large set of potential predictors of beta cell stress, measured as change in the proinsulin/insulin (PI/I) ratio, was conducted in a cohort of 235 outpatients with T2DM on stable treatment with oral hypoglycaemic agents or diet followed up for ~4 years (median value 3.9 years; interquartile range 3.8-4.1 years).

RESULTS

Overall, metabolic control deteriorated over time, with a significant increase in glycated haemoglobin (HbA1c; P < .0001), proinsulin (P < .0001), and PI/I ratio (P = .001), without significant changes in the homeostatic model assessment of insulin resistance. Multivariate regression analysis showed that for each 1% (10.9 mmol/mol) increase from baseline in HbA1c, the risk of beta cell stress increased by 3.8 times; for each 1% (10.9 mmol/mol) incremental increase in HbA1c during the study, risk of beta cell stress increased by 2.25 times that at baseline. By contrast, baseline anthropometric and clinical variables, lipid profile, inflammatory markers (PCR, IL-6), non-esterified fatty acids, and current therapies did not independently influence PI/I ratio variation during follow-up.

CONCLUSIONS

In this cohort of patients with T2DM, beta cell function progressively deteriorated despite current therapies. Among a large set of clinical and biochemical predictors, only baseline HbA1c levels and their deterioration overtime were associated with higher beta cell stress over time.

Insulin Resistance and the Risk of Diabetes and Dysglycemia in Korean General Adult Population

BACKGROUND

Insulin resistance is a major pathogenic hallmark of impaired glucose metabolism. We assessed the accuracy of insulin resistance and cut-off values using homeostasis model assessment of insulin resistance (HOMA-IR) to classify type 2 diabetes mellitus (T2DM) and dysglycemia according to age and sex.

METHODS

In this cross-sectional study, we analyzed 4,291 anti-diabetic drug-naïve adults (≥20 years) from the 6th Korea National Health and Nutrition Examination Survey in 2015. Metabolic syndrome (MetS) was defined by the modified National Cholesterol Education Program III guideline. Diagnosis of dysglycemia and T2DM were based on fasting glucose and glycosylated hemoglobin levels. The receiver operating characteristic curve and optimal cut-off values of HOMA-IR were assessed to identify T2DM/dysglycemia according to sex and were further analyzed by age.

RESULTS

Sex differences were found in the association of MetS and the different MetS components with T2DM/dysglycemia. The overall optimal cut-off value of HOMA-IR for identifying dysglycemia was 1.6 in both sex. The cut-off values for T2DM were 2.87 in men and 2.36 in women. However, there are differences in diagnostic range of HOMA-IR to distinguish T2DM according to sex and age, and the accuracy of HOMA-IR in identifying T2DM gradually decreased with age especially in women.

CONCLUSION

Insulin resistance is closely associated with the risk for T2DM/dysglycemia. The accuracy of HOMA-IR levels is characterized by sex- and age-specific differences in identifying T2DM. In addition to insulin resistance index, insulin secretory function, and different MetS components should be considered in the detection of early T2DM, especially in elderly.

Relationships of Insulin Action to Age, Gender, Body Mass Index, and Waist Circumference Present Diversely in Different Glycemic Statuses among Chinese Population

INTRODUCTION

To study the influence of different glycemic statuses on the relationship of insulin action to age, gender, body mass index (BMI), waist circumference (WC), and waist-to-height ratio (WHtR) among Chinese population.

METHODS

A total of 35,327 participants (17,456 males and 17,871 females) were included in this nationally representative cross-sectional study. Glycemic status was defined according to the 2010 American Diabetes Association criteria. Fasting insulin was measured by the chemiluminescence method.

RESULTS

Insulin and HOMA-IR levels were the highest in newly diagnosed diabetes and were lowest in normal fasting glucose (NFG) (P < 0.001). Insulin and HOMA-IR levels were higher in females (P < 0.001) than in males with previously diagnosed diabetes and impaired fasting glucose (IFG) and NFG, meanwhile decreased with age (P < 0.001) among IFG and NFG participants. As compared with participants with a BMI from 18.5 to 19.9, those in the lowest BMI category (<18.5) had a significantly elevated risk of IR (OR, 1.96; 95% CI, 1.01-3.80), as did those in the higher BMI categories among NFG participants. The risk of IR increased with WC and WHtR, and the response was linear (P < 0.001 for linear trend) for the participants with NFG but not in those with IFG.

CONCLUSIONS

Different glycemic statuses significantly affect the relationships of insulin action to age, gender, BMI, WC, and WHtR among Chinese population.

Development and Risk Factors of Type 2 Diabetes in a Nationwide Population of Women With Polycystic Ovary Syndrome

OBJECTIVE

Polycystic ovary syndrome (PCOS) is associated with insulin resistance and obesity. Prospective population-based data regarding development and possible predictors of type 2 diabetes (T2D) in PCOS are limited.

DESIGN

National Patient Register-based study.

METHODS

Patients with PCOS [PCOS Denmark and embedded cohort, PCOS Odense University Hospital (OUH)] and a control population with no previous diagnosis of T2D. PCOS OUH (N = 1,162) included premenopausal women with PCOS and standardized clinical and biochemical examination. PCOS Denmark (N = 18,477) included women with PCOS in the Danish National Patient Register. Three age-matched controls were included per patient (N = 54,680).

MAIN OUTCOME

T2D events according to diagnosis codes and filled medicine prescriptions.

RESULTS

The median (quartiles) follow-up was 11.1 (6.9 to 16.0) years. The hazard ratio (HR) with 95% confidence interval (CI) for development of T2D in PCOS Denmark was HR = 4.0 (95% CI, 3.7 to 4.3; P < 0.001), and the total event rate of T2D was 8.0 per 1000 person years in PCOS Denmark vs 2.0 per 1000 person years in controls (P < 0.001). The median age at diagnosis of T2D was 31 (26 to 37) years in PCOS Denmark vs 35 (27 to 44) years in controls (P < 0.001). In multiple regression analyses, body mass index, glycated hemoglobin, fasting blood glucose, 2-hour blood glucose, homeostasis model assessment of insulin resistance, and triglycerides were positively associated with development of T2D, whereas higher number of births was negatively associated with development of T2D.

CONCLUSION

The event rate of T2D was higher in PCOS compared with controls, and T2D was diagnosed at a younger age.

Insulin Receptor Isoforms in Physiology and Disease: An Updated View

The insulin receptor (IR) gene undergoes differential splicing that generates two IR isoforms, IR-A and IR-B. The physiological roles of IR isoforms are incompletely understood and appear to be determined by their different binding affinities for insulin-like growth factors (IGFs), particularly for IGF-2. Predominant roles of IR-A in prenatal growth and development and of IR-B in metabolic regulation are well established. However, emerging evidence indicates that the differential expression of IR isoforms may also help explain the diversification of insulin and IGF signaling and actions in various organs and tissues by involving not only different ligand-binding affinities but also different membrane partitioning and trafficking and possibly different abilities to interact with a variety of molecular partners. Of note, dysregulation of the IR-A/IR-B ratio is associated with insulin resistance, aging, and increased proliferative activity of normal and neoplastic tissues and appears to sustain detrimental effects. This review discusses novel information that has generated remarkable progress in our understanding of the physiology of IR isoforms and their role in disease. We also focus on novel IR ligands and modulators that should now be considered as an important strategy for better and safer treatment of diabetes and cancer and possibly other IR-related diseases.

Hyperproinsulinemia in obesity and in type 2 diabetes and its relation to cardiovascular disease

Disproportionately elevated fasting levels of proinsulin immunoreactive material (PIM)relative to insulin immunoreactivity (IRI) are a well-established abnormality in type 2 diabetes. Thesignificance of this abnormality has been investigated and discussed in several studies. Areas covered: The present review focuses on the role of proinsulin and its conversion intermediates inthe development of type 2 diabetes, obesity and insulin resistance, and the potential role as a marker ofcardiovascular risk, including the most important studies in this field. Expert commentary: The composition of plasma PIM is heterogeneous comprising des(31,32)-proinsulin,intact proinsulin and small amounts of des(64,65)-proinsulin. Disproportionate hyperproinsulinemiaseems to occur early in the development and before the diagnosis of type 2 diabetes, and seemsassociated to disease progression. Obesity and insulin resistance does not influence fasting PIM/IRI levels in type 2 diabetes. Fasting PIM/IRI levels in type 2 diabetes are closely associated with the degree of impairment in insulin secretory capacity. Different type 2 diabetes alleles have been described associated with elevated PIM/IRI levels. Recent data suggests that proinsulin and its conversion intermediates may have a role as markers of increased risk of cardiovascular disease in glucose intolerance and type 2 diabetes.

Relative levels of the proprotein and cleavage-activated form of circulating human anti-Müllerian hormone are sexually dimorphic and variable during the life cycle

Anti‐Müllerian hormone (AMH) is a gonadal hormone, which induces aspects of the male phenotype, and influences ovarian follicular recruitment. AMH is synthesized as a proprotein (proAMH), which is incompletely cleaved to the receptor‐competent AMH_N,C. AMH ELISAs have not distinguished between proAMH and AMH_N,C; consequently, the physiological ranges of circulating proAMH and AMH_N,C are unknown. A novel proAMH ELISA has been used to assay serum proAMH in humans. Total AMH was also measured, enabling the AMH_N,C concentration to be calculated. Stored serum from 131 boys, 80 younger, and 106 older men were examined, with serum from 14 girls and 18 women included for comparison. The mean levels of proAMH and AMH_N,C in pM were respectively: boys (253, 526), men (7.7, 36), elderly men (5.7, 19), girls (3.3, 15), and women (5.2, 27) (boys vs. men, P < 0.001; girls vs. women, P = 0.032). The proportion of proAMH as a percentage of total AMH (API) was approximately twofold higher in boys than men (P < 0.001) with little overlap between the ranges, with girls also exhibiting lesser cleavage of their AMH than women (P < 0.001). The API varied within each population group. In young men, the API did not correlate with circulating levels of the other testicular hormones (testosterone, InhB, and INSL3). In conclusion, the cleavage of circulating AMH varies extensively within the human population, with most individuals having significant levels of proAMH. The physiological and clinical relevance of circulating proAMH needs to be established.

Long-term activation of PKA in β-cells provides sustained improvement to glucose control, insulin sensitivity and body weight

Type 2 diabetes is associated with obesity, insulin resistance and β-cell failure. Therapeutic aims are to reduce adiposity, improve insulin sensitivity and enhance β-cell function. However, it has been proposed that chronically increasing insulin release leads to β-cell exhaustion and failure. We previously developed mice to have increased activity of the cAMP-dependent protein kinase (PKA), specifically in β-cells (β-caPKA mice). β-caPKA mice have enhanced acute phase insulin release, which is the primary determinant of the efficacy of glucose clearance. Here these mice were used to determine the sustainability of enhanced insulin secretion, and to characterize peripheral effects of enhanced β-cell function. Increased PKA activity was induced by tamoxifen administration at 10 weeks of age. Male mice were aged to 12 months of age and female mice to 16 months. Glucose control in both male and female β-caPKA mice was significantly improved relative to littermate controls with ad libitum feeding, upon refeeding after fasting, and in glucose tolerance tests. In female mice insulin release was both greater and more rapid than in controls. Female mice were more insulin sensitive than controls. Male and female β-caPKA mice had lower body weights than controls. DEXA analysis of male mice revealed that this was due to reduced adiposity and not due to changes in lean body mass. This study indicates that targeting β-cells to enhance insulin release is sustainable, maintains insulin sensitivity and reduces body weight. These data identify β-cell PKA activity as a novel target for obesity therapies.

High-fat diet induced obesity primes inflammation in adipose tissue prior to liver in C57BL/6j mice

Metabolic inflammation in adipose tissue and the liver is frequently observed as a result of diet-induced obesity in human and rodent studies. Although the adipose tissue and the liver are both prone to become chronically inflamed with prolonged obesity, their individual contribution to the development of metabolic inflammation remains speculative. Thus, we aimed to elucidate the sequence of inflammatory events in adipose and hepatic tissues to determine their contribution to the development of metabolic inflammation and insulin resistance (IR) in diet-induced obesity. To confirm our hypothesis that adipose tissue (AT) inflammation is initiated prior to hepatic inflammation, C57BL/6J male mice were fed a low-fat diet (LFD; 10% kcal fat) or high-fat diet (HFD; 45% kcal fat) for either 24, 40 or 52 weeks. Lipid accumulation and inflammation was measured in AT and liver. Glucose tolerance was assessed and plasma levels of glucose, insulin, leptin and adiponectin were measured at various time points throughout the study. With HFD, C57BL/6j mice developed a progressive obese phenotype, accompanied by IR at 24 and 40 weeks of HFD, but IR was attenuated after 52 weeks of HFD. AT inflammation was present after 24 weeks of HFD, as indicated by the increased presence of crown-like structures and up-regulation of pro-inflammatory genes Tnf, Il1β, Mcp1 and F4/80. As hepatic inflammation was not detected until 40 weeks of HFD, we show that AT inflammation is established prior to the development of hepatic inflammation. Thus, AT inflammation is likely to have a greater contribution to the development of IR compared to hepatic inflammation.

Dyslipidemia and reduced total antioxidant status in young adult Saudis with prediabetes

AIMS

Lifestyle related noncommunicable health conditions are having an increasingly negative impact on the health. This study aimed to assess the lipid profile, total antioxidant capacity, and the lifestyle predictors of conversion to prediabetes in young Saudis with prediabetes.

MATERIALS AND METHODS

One hundred and twenty-one young Saudis with fasting plasma glucose (<125 mg/dl) enrolled in this study who further categorized into normal glucose tolerance "NGT" group (n=86) and prediabetes group (IFG; n=08/IGT; n=27) based on American Association criteria. Venous blood samples were collected at fasting and 2h postprandial from participants. Chemistry parameters and total antioxidant status (TAS) were assayed by standard procedures. Questionnaires were applied to collect information including demographic characteristics, physical activity, and family history to diabetes. Statistical analysis was performed using SPSS version 17.

RESULTS

Compared to NGT subjects, the prediabetics characterized by marked obesity (p=.027), visceral obesity (p=.002), dyslipidemia, significantly increased HbA1c (p=.003), reduced TAS (p<.001), more sedentary lifestyle (p=.010). Positive correlations were documented between FPG, 2-h plasma glucose and HbA1c, BMI, WC, TC, LDL cholesterol, TG while negative correlations with HDL cholesterol, TAS.

CONCLUSION

The current study reported that prediabetes condition (in young adult Saudis) was associated with dyslipidemia, reduced total antioxidant status, obesity, central obesity, and physical inactivity compared to those with normoglycemia. Lifestyle modifications (through weight loss, regular physical activity, and healthy diet) should be encouraged especially among young Saudis to prevent the progression to type 2 diabetes and its complications from prediabetes state.

Factors associated with beta-cell dysfunction in type 2 diabetes: the BETADECLINE study

Aims

Beta-cell dysfunction is an early event in the natural history of type 2 diabetes. However, its progression is variable and potentially influenced by several clinical factors. We report the baseline data of the BetaDecline study, an Italian prospective multicenter study on clinical predictors of beta-cell dysfunction in type 2 diabetes.

Materials and Methods

Clinical, lifestyle, and laboratory data, including circulating levels of inflammatory markers and non-esterified fatty acids, were collected in 507 type 2 diabetic outpatients on stable treatment with oral hypoglycemic drugs or diet for more than 1 year. Beta-cell dysfunction was evaluated by calculating the proinsulin/insulin ratio (P/I).

Results

At baseline, the subjects in the upper PI/I ratio quartile were more likely to be men and receiving secretagogue drugs; they also showed a borderline longer diabetes duration (P = 0.06) and higher serum levels of glycated hemoglobin (HbA_1c), fasting blood glucose, and triglycerides. An inverse trend across all PI/I quartiles was noted for BMI and serum levels of total cholesterol (T-C), LDL-C, HDL-C and C reactive protein (CRP), and with homeostatic model assessment (HOMA-B) and HOMA of insulin resistance (HOMA-IR) values (P<0.05 for all). At multivariate analysis, the risk of having a P/I ratio in the upper quartile was higher in the subjects on secretagogue drugs (odds ratio [OR] 4.2; 95% confidence interval [CI], 2.6–6.9) and in the males (OR 1.8; 95% CI, 1.1–2.9).

Conclusions

In the BetaDecline study population, baseline higher PI/I values, a marker of beta-cell dysfunction, were more frequent in men and in patients on secretagogues drugs. Follow-up of this cohort will allow the identification of clinical predictors of beta-cell failure in type 2 diabetic outpatients.

Proinsulin and age in general population

OBJECTIVE

The objective of this study was to assess the relationship between fasting proinsulin (PI) and age in general population and to determine whether there are differences regarding this association in obese and non-obese persons.

METHODS

A random population-based sample (n=656) of Romanians (26-80 years) living in Bucharest, Romania was studied; 432 persons had diabetes and they were not analyzed in this paper. Circulating levels of fasting plasma glucose (FPG), fasting plasma insulin (FPI), fasting plasma proinsulin (FPP), fasting plasma C-peptide, HbA1c, lipid profile, creatinine, urea were measured. The homeostasis model assessment of insulin resistance (HOMA-IR), HOMA-B, and Quicki index were also calculated.

RESULTS

For all participants proinsulin was the highest in the third quartile of the age group (59-67 years), with a median proinsulin of 5.8 pmol/L. Subsequently, proinsulin increased with age, from 2.6 pmol/L for participants aged 20-51 years, to 4.7 pmol/L for participants aged 51-59 years; proinsulin levels decreased in the upper quartile 4.8 pmol/L for those aged over 67 years. In sex-specific analyses, proinsulin increased with age for both men and women, except for those in the upper quartile. The prevalence of the obesity was 30.4% (n=68); obesity prevalence did not increase with age (p=0.26). Fasting proinsulin levels significantly increased with body mass index (BMI) category from lean (n=67, 2.9 pmol/L) to overweight (n=89, 4.5 pmol/L) and obese (n=69, 6.63 pmol/L) (p<0.0001).

CONCLUSIONS

Our study has demonstrated a close association between age and elevated proinsulin and proinsulin/insulin ratio in general population.

Relationship between major depression and insulin resistance: does it vary by gender or race/ethnicity among young adults aged 20-39 years?

BACKGROUND

To examine the relationship between major depression and insulin resistance by gender and race/ethnicity among young adults without diabetes mellitus.

METHODS

Secondary analyses of cross-sectional data from the National Health and Nutrition Examination Survey 1999-2008 were performed (n = 2265). Major depression was measured by the Composite International Diagnostic Interview and the Patient Health Questionnaire 9. Insulin resistance was measured by the homeostasis model assessment of insulin resistance. Multivariate logistic regression analyses adjusted for risk factors of insulin resistance were conducted.

RESULTS

There was a significant negative association between major depression and insulin resistance among men. For women, no significant association was found. There was no significant interaction between race/ethnicity and major depression on insulin resistance (Wald χ(2) = 4.2927, P = 0.2315). Body mass index (BMI) and waist circumference (WC) were significantly associated with insulin resistance among both men (odds ratio [OR] 1.255, 95% confidence interval [CI] 1.195-1.318 for BMI; OR 1.095, 95% CI 1.076-1.115 for WC) and women (OR 1.220, 95% CI 1.182-1.260 for BMI; OR 1.084, 95% CI 1.064-1.105 for WC).

CONCLUSIONS

There are gender differences in the relationship between major depression and insulin resistance among adults aged 20-39 years. No evidence was found to support the role of race/ethnicity in this relationship. Health care professionals should be aware of risk factors for insulin resistance and develop interventions to help prevent the progression of insulin resistance to type 2 diabetes mellitus.

Effect of vildagliptin compared to glimepiride on postprandial proinsulin processing in the β cell of patients with type 2 diabetes mellitus

This study compared the effect of Glimepiride versus Vildagliptin on β-cell function and the release of intact proinsulin (PI) in patients with type 2 diabetes mellitus. Patients on metformin monotherapy were randomized to add on treatment with Vildagliptin or Glimepiride. A standardized test meal was given at baseline, after 12 and 24 weeks of treatment. Insulin, PI and blood glucose values were measured in the fasting state and postprandial for 300 min. Fasting PI levels significantly decreased in the Vildagliptin group. The area under the curve for the postprandial release of PI decreased during Vildagliptin and increased during Glimepiride treatment. The proinsulin to insulin ratio declined in the Vildagliptin group, whereas it did not change significantly in the Glimepiride group. Addition of Vildagliptin to ongoing Metformin treatment reconstitutes the disproportionality of the proinsulin to insulin secretion from the β cell.

Association of proinsulin and hepatic steatosis in a random, population-based sample

OBJECTIVE

Proinsulin may represent a predictive marker for assessing insulin resistance and reduced β-cell function. The objective of this study was to investigate the association between hepatic steatosis, proinsulin and other parameters in a random, population-based sample.

DESIGN

Cross-sectional study, conducted in south-western Germany.

METHODS

Upper abdominal ultrasound examinations were performed in 343 subjects (147 females, 196 males; average age 40.0±11.5 years). Proinsulin, the proinsulin-to-insulin ratio and other laboratory parameters were determined, and the BMI, waist-to-hip ratio (WHR) and other anthropometric data were documented.

RESULTS

HEPATIC STEATOSIS WAS OBSERVED IN 80 SUBJECTS (23.3%: 29.6%, males; 15.0%, females). Multivariate analysis showed an association with hepatic steatosis for male gender (P=0.0212), advancing age (P=0.0241), elevated BMI (P<0.0001), elevated WHR (P=0.0024), alanine aminotransferase (P=0.0046), proinsulin (P=0.0403) and proinsulin-to-insulin ratio (P=0.0116).

CONCLUSIONS

There is an association between elevated proinsulin concentrations and hepatic steatosis.

Proinsulin binds with high affinity the insulin receptor isoform A and predominantly activates the mitogenic pathway

Proinsulin is generally regarded as an inactive prohormone because of its low metabolic activity. However, proinsulin appears to regulate embryo development in animal models. In this study, we evaluated whether proinsulin may differentially bind to and activate the two insulin receptor (IR) isoforms (IR-A and IR-B), because IR-A is a relatively low-specificity receptor that is prevalent in fetal and cancer cells and is able to mediate the growth effects of IGF-II. Mouse R(-) fibroblasts devoid of IGF-I receptor (IGF-IR) and stably transfected with cDNA encoding either human IR-A or IR-B (R(-) /IR-A and R(-) /IR-B cells) were used. Three human cancer cell lines were also studied. We found that proinsulin stimulated phosphorylation of IR-A with an EC(50) of 4.5 ± 0.6 nm and displaced [(125)I]insulin from IR-A with a similar EC(50). In contrast, proinsulin EC(50) values for stimulation of IR-B phosphorylation and for [(125)I]insulin displacement from IR-B were approximately 7-fold higher. Proinsulin did not bind or activate IGF-IR or IR/IGF-IR hybrids. Via IR-A, proinsulin activated the ERK/p70S6K pathway to a similar degree as insulin but elicited a weaker Akt response. Despite its low metabolic activity, proinsulin was almost equipotent as insulin in inducing cell proliferation and migration in cells expressing various IR-A levels. In conclusion, proinsulin is a selective IR-A ligand and may induce biological effects through this IR isoform.